A gas turbine engine may be used to power various types of vehicles and systems. A particular type of gas turbine engine that may be used to power an aircraft is a turbofan gas turbine engine. A turbofan gas turbine engine may include, for example, a fan section, a compressor section, a combustor section, a turbine section, and an exhaust section. The fan section is positioned at the front of the engine, and includes a fan that induces air from the surrounding environment into the engine and accelerates a fraction of this air toward the compressor section. The remaining fraction of induced air is accelerated into and through a bypass plenum, and out the exhaust section.
The compressor section is configured to raise the pressure of the air to a relatively high level and includes an impeller that has a plurality of blades extending therefrom that accelerate and compress the air. The compressed air then exits the compressor section, and is energized by the combustor section. Next, the energized air is directed into the turbine section, which includes a rotor and a plurality of turbine blades that are mounted thereto. The air impinges the turbine blades and causes the rotor to rotate and to generate energy.
To protect the rotor blades from tip loss, a suitably sized annular shroud surrounds the rotor blades. Typically, the annular shroud and blades define a radial clearance gap therebetween that is sufficiently large to allow the blades to rotate without contacting the shroud, while small enough to optimize engine efficiency. Thus, maintaining the annular shroud in a particular position relative to the blades is preferable.
In one positioning configuration, the annular shroud is coupled to a cylindrical flowpath housing that is mounted around the rotor. Both the turbine shroud and flowpath housing include pilots that mate with each other to ensure proper radial positioning of the shroud on the flowpath housing. In many cases, the shroud pilot is an annular protruding ring formed on the shroud inner surface and the flowpath housing pilot is a corresponding structure formed on the flowpath housing outer surface. In many gas turbine engine configurations, the flowpath housing also includes a plurality of support struts that radially extend at least partially therethrough.
During engine operation, exposure to the energized air from the combustor section may cause the flowpath housing struts to expand radially outwardly at a rate that is faster than the radial expansion rate of the cylindrical flowpath housing. Accordingly, the flowpath housing may become misshapen, and may consequently form a rectangular-shaped component. As a result, the annular shroud may become misshapen, thereby undesirably altering the configuration of the clearance gap and the positioning of the shroud relative to the flowpath housing.
Therefore, there is a need for a shroud that allows the flowpath housing to radially expand without compromising the configuration of the clearance gap. Additionally, it is desirable for the shroud to be simple and inexpensive to manufacture and to implement.